Investment casting technique presents more advantages in the production of accuracy and versatility components. The mechanical performance of the ceramic shell is crucial to the quality of the castings. The slurry parameters can affect the properties of the ceramic shell. The purpose of this paper is to investigate the physical properties of primary slurry for titanium and titanium alloy investment casting. Three different slurries (ZrO2, Y2O3 and Al2O3) were evaluated respectively by comparing the parameters: viscosity, bulk density, particle size distribution, thixotropy and suspension percentage of slurries. The results show that the physical properties of primary slurry were mostly determined by the type and content of refractory materials. Refractory particle morphology and the particle size distribution affect slurry rheology and viscosity.